The invention relates to processes and apparatus for melt spinning polymeric filaments at high speeds, for example over 3,500 meters per minute (mpm) for polyester filaments.
Most synthetic polymeric filaments, such as polyesters, are melt-spun, i.e., they are extruded from a heated polymeric melt. In current processes, after the freshly extruded molten filamentary streams emerge from the spinneret, they are quenched by a flow of cooling gas to accelerate their hardening. They can then be wound to form a package of continuous filament yarn or otherwise processed, e.g., collected as a bundle of parallel continuous filaments for processing, e.g., as a continuous filamentary tow, for conversion, e.g., into staple or other processing.
It has long been known that polymeric filaments such as polyesters, can be prepared directly, i.e., in the as-spun condition, without any need for drawing, by spinning at high speeds of the order of 5 km/nin or more. Hebeler disclosed this for polyesters in U.S. Pat. No. 2,604,667.
There have been essentially two basic types of quench systems in general commercial use. Cross-flow quench has been favored and used commercially. Cross-flow quench involves blowing cooling gas transversely across and from one side of the freshly extruded filamentary array. Much of this cross-flow air passes through and out the other side of the filament array. However, depending on various factors, some of the air may be entrained by the filaments and be carried down with them towards a puller roll, which is driven and is usually at the base of each spinning position. Cross-flow has generally been favored by many fiber engineering firms as puller roll speeds (also known as xe2x80x9cwithdrawal speedsxe2x80x9d and sometimes referred to as spinning speeds) have increased because of a belief that xe2x80x9ccross-flow quenchxe2x80x9d provides the best way to blow the larger amounts of cooling gas required by increased speeds or through-put.
Another type of quench is referred to as xe2x80x9cradial quenchxe2x80x9d and has been used for commercial manufacture of some polymeric filaments, e.g., as disclosed by Knox in U.S. Pat. No. 4,156,071, and by Collins, et al. in U.S. Pat. Nos. 5,250,245 and 5,288,553. In this type of xe2x80x9cradial quenchxe2x80x9d the cooling gas is directed inwards through a quench screen system that surrounds the freshly extruded filamentary array. Such cooling gas normally leaves the quenching system by passing down with the filaments, out of the quenching apparatus. Although, for a circular array of filaments, the term xe2x80x9cradial quenchxe2x80x9d is appropriate, the same system can work essentially similarly if the filamentary array is not circular, e.g., rectangular, oval, or otherwise, with correspondingly-shaped surrounding screen systems that direct the cooling gas inwards towards the filamentary array.
In the 1980""s, Vassilatos and Sze made significant improvements in the high-speed spinning of polymeric filaments and disclosed these and the resulting improved filaments in U.S. Pat. Nos. 4,687,610, 4,691,003, 5,141,700, and 5,034,182. These patents describe gas management techniques, whereby gas surrounded the freshly extruded filaments to control their temperature and attenuation profiles. While these patents describe breakthroughs in the field of high-speed spinning, there is a continuing desire to increase yarn-spinning productivity through increased withdrawal speeds, while maintaining at least comparable or improved yarn properties.
In accordance with these needs there is provided processes and apparatuses for spinning polymeric filaments.
Accordingly to one aspect of the present invention, there is provided a melt spinning apparatus for spinning continuous polymeric filaments, comprising:
a first stage gas inlet chamber adapted to be located below a spinneret and a second stage gas inlet chamber located below the first stage gas inlet chamber wherein the first and second stage gas inlet chambers supply gas to the filaments to control temperature of the filaments; and
a tube located below the second stage gas inlet chamber for surrounding the filaments as they cool, the tube including an interior wall having a converging section, followed by a diverging section.
In accordance with yet another aspect-of the present invention there is provided a melt spinning apparatus for spinning continuous polymeric filaments, comprising:
a housing adapted to be located below a spinneret;
a first stage chamber and a second stage chamber, each formed in an inner wall of the housing;
a first stage gas inlet for supplying gas to the first stage chamber;
a second stage gas inlet for supplying gas to the second stage chamber;
a wall attached to the inner wall at a lower portion of the first stage chamber to separate the first stage chamber from the second stage chamber;
a quench screen centrally positioned in the first stage chamber, wherein the apparatus is adapted such that pressurized gas is blown inwardly from the first stage gas inlet through the first stage chamber into a zone formed in the interior wall of the quench screen;
an inner wall disposed below the quench screen and between the first stage gas inlet and the second stage gas inlet;
a first stage converging section formed in the interior of the inner wall;
a perforated tube disposed below the first stage converging section and between the first stage gas inlet and the second stage gas inlet, the perforated tube being located centrally within the second stage chamber;
an inner wall located below the perforated tube;
a tube located in the interior of the inner wall, the tube including an interior wall surface having a second stage converging section located within the second stage chamber, and a diverging section located at the exit of the second stage chamber; and
optionally a converging cone having perforated walls located at the exit of the tube.
In accordance with another aspect of the present invention there is provided a melt spinning process for spinning continuous polymeric filaments, comprising passing a heated polymeric melt in a spinneret to form filaments; providing a gas to the filaments from a gas inlet chamber located below the spinneret in a first stage; providing a gas to the filaments from a gas inlet chamber in a second stage; passing the filaments to a tube located below the gas inlet chambers, wherein said tube comprises an interior wall having a first converging section; and passing the filaments through the tube.
In accordance with another embodiment of the present invention there is provided a melt spinning apparatus for spinning continuous polymeric filaments, comprising a tube to surround the filaments; two or more gas inlet chambers adapted to be located below a spinneret and which supply gas to the filaments to control the temperature of the filaments and further comprising at least one exhaust stage adapted to remove air from the apparatus.
In accordance with yet another aspect of the present invention there is provided a melt spinning process for spinning continuous polymeric filaments, comprising:
passing a heated polymeric melt in a spinneret to form filaments;
providing a gas to the filaments from a gas inlet chamber located below the spinneret in a first stage;
providing a means for gas to vent from at least one gas exhaust chamber located below the first stage;
passing the filaments through a tube located below the gas inlet chamber, wherein said tube comprises an interior wall having a first converging section that increases air speed; and
allowing the filaments to exit the tube.
In yet another embodiment of the present invention there is provided a melt spinning apparatus for spinning continuous polymeric filaments, comprising a tube for surrounding the filaments; one or more gas inlets adapted to be located below a spinneret, at least one inlet including means to supply gas to the filaments above atmospheric pressure to control temperature of the filaments; and a vacuum exhaust to remove gas.
In another aspect of the present invention there is further provided a melt spinning apparatus for spinning continuous polymeric filaments, comprising a tube located below a gas inlet chamber for surrounding the filaments as they cool, the tube including an interior wall including a converging section for accelerating gas, followed by a diverging section.
In another embodiment of the present invention there is further provided a melt spinning apparatus for spinning continuous polymeric filaments, comprising:
a housing adapted to be located below a spinneret;
a first stage chamber, a second stage chamber, and a third stage chamber each formed in an inner wall of the housing;
a first stage gas inlet for supplying gas to the first stage chamber;
a second stage gas inlet for supplying or exhausting gas to or from the second stage chamber;
a third stage gas inlet for supplying gas to the third stage chamber; and
a converging section in at least one of the stages or after the third stage, for accelerating gas.
In an embodiment of the present invention there is also provided a melt spinning apparatus for spinning continuous polymeric filament, comprising
two or more gas inlet chambers adapted to be located below a spinneret and which supply gas to the filaments to control the temperature of the filaments;
at least one gas inlet for supplying gas to one or more of the inlet chambers;
at least one perforated annular plate separating the inlet chambers; and
a tube for surrounding the filaments as they cool, the tube including an interior wall having a converging section, optionally followed by a diverging section.
In one aspect of the present invention there is also provide a method for cooling melt spun polyester filaments comprising providing a cooling gas to the filaments in at least two stages, and accelerating the gas between the stages.
In another aspect of the present invention there is provided a melt spinning apparatus for spinning continuous polymeric filament, comprising a tube for surrounding filaments, the tube including a diverging section with perforations and one or more gas inlets.
In yet another aspect of the present invention there is provided a melt spinning apparatus for spinning continuous polymeric filament, comprising a tube for surrounding filaments, one or more gas inlets, a means to introduce super atmospheric gas to at least one inlet, and a means to introduce ambient air to at least one inlet.
Further objects, features and advantages of the invention will become apparent from the detailed description that follows.